A large advance in geology in the advent of the 20th century was the ability to use ratios of radioactive isotopes to find the amount of time that has passed since a rock passed through a particular temperature. These methods work by measuring the time since a particular mineral grain cooled through its closure temperature, at which point the different radiometric isotopes stop diffusing out of the crystal lattice.
The advent of isotopic dating changed the understanding of geologic time. Before, geologists could only use fossils to date sections of rock relative to one another. With isotopic dates, absolute dating became possible, and these absolute dates could be applied fossil sequences in which there was datable material, converting the old relative ages into new absolute ages.
Geologists have used radioactive decay to establish the age of the Earth at about 4.54 billion (4.5x109) years and the age of the oldest planetary material (Carbonaceous Chondrite meteorites) at 4.567 billion years
No comments:
Post a Comment